Method of forming bellows



J. LANGLET ET AL METHOD OF FORMING BELLOWS May 6, 1969 Sheet Filed April4, 1966 F162 PRIOR ART PRIOR ART mlorr Milk:

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May 6, 1969 LANGLET EI'AL 3,442,005

METHOD OF FORMING BELLOWS Filed April 4. 1966 Sheet 3 of 2 FIG. 5

United States Patent 3,442,005 METHOD OF FORMING BELLOWS JeanLanglet,Neuilly-sur-Seine, and Joseph Gustave Etienne Andre, Toulouse, France,assignors to Callisto, La Garenne and Sud-Aviation, Paris,

France, French companies Filed Apr. 4, 1966, Ser. No. 539,780 Claimspriority, applicaiign France, Apr. 3, 1965,

1 Int. Cl. F16j 3/00 US. Cl. 29-454 3 Claims ABSTRACT OF THE DISCLOSUREThe present invention relates to bellows, and more particularly to abellows composed of a plurality of identical annular parts bondedtogether in a novel manner to withstand high temperatures and a highpressure.

Two basic types of bellows are known in the art.

One type of bellows is known in which a thin walled tube is corrugatedby a hydraulic process into a bellows. The alloys from which the thinwalled tubes are formed which are subsequently transformed into abellows necessarily have to have a ductility and stretchabilitysufficient to sustain the considerable cold deformation of the tube intoa bellows while maintaining after the formation acceptable mechanicalcharacteristics.

Therefore, only certain alloys such as tombac, Monel or stainless steelmay be used for this purpose and none of these alloys is structurallyhardenable by heat treatment. Therefore the bellows produced from thesealloys are not adapted to resist at the same time high temperatures, ahigh pressure while being subjected to a corrosive atmosphere so as tooperate trouble-free for a considerable time under adverse operatingconditions. In addition, these bellows usually have a stroke less than20% of their free length and this stroke is preferably performed bycontraction of the bellows.

The second basic type of known bellows comprises a plurality of annulardisks welded at the inner and outer peripheral edges to each other. Agreat number of metal alloys can be used for manufacutring a bellows ofthis type and especially alloys which can be structurally hardened byheat treatment may be used. The bellows of the second type willtherefore have mechanical characteristics improved over the bellows ofthe first mentioned type and the performance of the bellows of thesecond type will be superior in many respects with regard to the bellowsof the first type. Nevertheless the welded portions of the second typeof bellows represent zones of fragility.

For certain applications it is not necessary that the bellows can expandto a considerable extent in longitudinal direction or that they areflexible to a considerable extent in a direction transverse to theiraxes, but it is necessary that these bellows operate under severeoperating conditions, that is at high temperature, for example, at atemperature of 650 C. and that they have to withstand high pressuressuch as for instance 20 kg. per cm.*. In addition, the bellows in suchapplications may be subjected to strong internal turbulences andvibrations. The

known bellows of the two constructions above mentioned will go out ofservice under such operating conditions in a short time either due torupture of the thin metal wall of the first mentioned type of bellows ordue to bursting of the bellows of the second type at the welded edgesthereof.

Various attempts have been made to overcome the shortcomings of the twotypes of bellows mentioned above, but the constructions known in the artto improve these bellows have not worked out satisfactorily in practice.

It is an object of the present invention to provide for a bellows whichavoids the shortcomings of the bellows known in the art mentioned above.

It is an additional object of the present invention to provide for abellows which is composed of a plurality of elements aligned along acommon axis, bonded together, and constructed and arranged in such amanner so as to withstand high pressure especially internal pressurewithout bursting.

It is a further object of the present invention to provide for a methodof manufacturing such bellows in a simple and efiicient manner.

With these objects in view, the bellows according to the presentinvention mainly comprises a plurality of superimposed thin walledelements having surfaces of revolution and being aligned along a commonaxis with each other, each of the elements having in an axial crosssection a substantially U-shaped configuration with the concave side ofsaid U-shaped cross section facing the common axis, wherein adjacentelements abut against each other and being bonded to each other alongthe inner peripheral edges thereof. The plurality of elements abovementioned is preferably formed from sheet metal and the elements arebonded to each other preferably by welding along the inner peripheraledges thereof.

Preferably, the U-shaped cross section comprises a semi-circular portionand a pair of substantially parallel leg portions tangential to saidsemicircular portion and projecting therefrom toward the axis of thebellows.

In such a construction, high internal pressure will not lead todestruction of the bond between adjacent elements since the higher theinternal pressure will be the higher will be the pressure at which theportions of adjacent elements which abut against each other are pressedagainst each other.

According to a preferred method of forming the bellows according to thepresent invention, a plurality of annular sheet members are firstformed, for instance by stamping and each of the annular sheet membersis then formed into a substantially cup-shaped configuration having abottom portion with a central opening and an annular rim portionprojecting to one side of the bottom portion and joined thereto along acurved portion. Subsequently thereto the rim portion is bent towards thebottom portion so as to form from the rim portion a second curvedportion forming a continuation of the first mentioned curved portion andhaving the same radius of curvature as the latter, and a flat portionsubstantially parallel to the bottom portion and overlapping the latter.The thus-formed elements may be considered as toric shells having flatborder portions. After forming a plurality of such toric shells, thesame are superimposed upon each other abutting against each other alongthe flat border portions and subsequently thereto the abutting portionsof the elements are welded to each other along the inner peripheriesthereof. The welding is preferably performed as an autogenous welding inan inert gas atmosphere, especially in an atmosphere of argon.

End members of appropriate shape may be connected to the opposite endsof the thus formed bellows and these end members may be connected to theinner periphery of the opposite end elements forming the bellows, or oneor both of the end elements forming the bellows may have a free endportion in the form of a cylinder to the outer or inner surface thereofthe connecting member may be fixed, for instance likewise by welding.

A bellows of the aforementioned kind can be manufactured from a greatveriety of alloys, especially from alloys which may be hardened by heattreating.

The bellows according to the present invention has a great number ofadvantages over the bellows according to the above discussed prior art.The bellows according to the present invention may be manufactured fromthe plurality of superimposed toric shells in a very efficient mannerand therefore at reasonable cost. The bellows according to the presentinvention will have a movability in longitudinal and transversedirection which closely approaches that of the bellows of the firstmentioned kind. The shape of the bellows according to the presentinvention is especially adapted for the provision of internal orexternal guide means and means to prevent turbulence in the exterior ofthe bellows or vibration thereof. In addition, the bellows according tothe present invention has a remarkable resistance against high internalpressurex even if applied under additional especially severe conditionssuch as temperatures higher than 650 C. or maintenance of the bellows ina strongly corrosive atmosphere. Experience has shown that the bellowsaccording to the present invention will withstand such severe operatingconditions in a perfect manner.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

FIGS. 1 and 2 are axial cross sections through bellows according to theprior art;

FIG. 3 is an axial cross section through a bellows according to thepresent invention;

FIGS. 4a, 4b and 4c are axial cross sections and respectively illustratesuccessive steps of forming the toric shells from which the bellowsaccording to the present invention are made; and

FIG. 5 is a top view of a multipart form for forming the toric shells.

The bellows 1 shown in FIG. 1 is a bellows according to the prior art inwhich a thin walled tube is corrugated in a manner known to form thebellows 1 illustrated in FIG. 1 therefrom. FIG. 2 likewise illustrates abellows according to the prior art and the bellows 2 shown in FIG. 2 iscomposed of a plurality of substantially frustoconical disks 3 which arewelded at the inner and outer peripheral edges 4 and 5 to each other.Internal pressure in the bellows 2 will tend to spread the radiallyoutwardly extending portions of adjacent disks apart so that rupturealong the outer edges 5 may easily occur.

FIG. 3 illustrates an axial cross section through a bellows according tothe present invention. As can be seen from FIG. 3 the bellows accordingto the present invention comprises a plurality of elements or shells 7wherein each of the shells 7 has a surface of revolution about the axisX-X which in an axial cross section has a substantially U-shapedconfiguration with the concave side of the U-shaped cross section facingthe aforementioned axis. More precisely each U-shaped cross sectioncomprises a semi-circular portion 8 and a pair of substantially parallelleg portions 9 tangential to the aforementioned semicircular portion andprojecting therefrom substantially normal to the axis X-X' towards thelatter. Each shell 7 is therefore substantially in the form of asemitore having a concave side facing the axis thereof and extendingtangentially by two flat annular portions.

The shells 7 are preferably made from annular disks stamped out of sheetmetal. The annular disks are then formed for instance in a press into asubstantially cupshaped member as shown in FIG. 4a having asubstantially fiat bottom portion with a central opening and an annularrim portion projecting to one side from the bottom portion and joinedthereto along a curved portion so as to present in cross section aconfiguration of a rounded L 7a as shown in FIG. 4a. A bending form 20having three parts 20a, 20b, and 20c, as shown in FIG. 5, is then placedin the interior of the cup-shaped member, and as shown in FIG. 5 thepart 20a of the form 20 is constructed in such a manner that it can bewithdrawn into the central frustoconical opening 21 of the three partform 20. A frustoconical member 22 is then placed into the centralopening 21 of the three part form to hold the outer toric surfacethereof in engagement with the inner surface of the cut-shaped member.

Subsequently thereto the rim portion of the cup-shaped member is bent at7b, as shown in FIG. 4b over the curved surface of the three part moldand finally the upper portion of the rim of the cup-shaped member ispressed against the upper substantially flat surface of the three partform 20 so as to obtain the toric shell 7 as shown in FIG. 40.

After the shell 7 is thus finished the central core 22 is withdrawn fromthe three part mold and afterwards the part 20a is withdrawn into thecentral opening of the three part mold 20 whereupon the other two parts20b and 200 may also be withdrawn from the interior of the shell 7.

The above manner of manufacturing the shell 7 is given only by way of anexample and obviously the shell may be manufactured in various differentother ways.

After a plurality of shells 7 is manufactured, for instance in theabove-described manner, the shells are superimposed upon each other,aligned along a common axis, with the bottom portion of one shellabutting against the flat top portion of the shell adjacent thereto.Subsequently thereto the abutting portions of the shells are fixedlyconnected together for instance by autogenous welding in an inert gasatmosphere, for instance in an atmosphere of argon. The weld seams areproduced along the inner peripheries 10 of the shells.

In this way a bellows is produced which is adapted to withstand greatinterior pressures, since in the thus obtained construction an increasedpresesure in the interior of the bellows will press the leg portions 9of adjacent shells 7 with increased pressure against each other so thatthe weld seams 10 at the inner peripheries of the shells 7 will not beaffected by the increased pressure in the interior of the shells andevidently the bellows according to the present invention is adapted towithstand a much greater internal pressure than the bellows according tothe prior art as shown in FIG, 2 in which an increased interior pressurewill tend to press the outer peripheral portions of the frustoconicaldisks 3 away from each other so that the weld seams at the outerperiphery of these disks are liable to burst as the interior pressure inthe bellows increases.

To connect the bellows 6 shown in FIG. 3 to another machine element, anend member 11 as shown in FIG. 3 may be attached to the lowermost of theshells 7, for instance by welding the bottom portion of the lowermostshell 7 along the inner periphery thereof to the end member 11. A member12 having an upper cylindrical portion may be attached in the samemanner to the uppermost of the shells 7, as shown in FIG. 3, and themember 12 may serve to attach thereto in any convenient manner, forinstance likewise by welding, a connecting member not shown in FIG. 3thereto.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofbellows differing from the types described above.

While the invention has been illustrated and described as embodied in abellows formed by a plurality of substantially toric shells weldedtogether, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

For instance, if the bellows has to withstand an external pressure thetoric shells may be arranged so that the concave sides thereof face awayfrom the axis of the bellows.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A method of forming a bellows composed of a plurality of superimposedthin-walled elements defined by surfaces of revolution and being alignedalong a common axis and having each in axial cross-section asubstantially U-shaped configuration, said method comprising the stepsof forming from bendable but form-retaining sheet metal a plurality ofsubstantially flat annular sheet metal members; bending saidsubstantially fiat annular sheet metal members into annular elements ofsubstantially U-shaped cross-section having each a pair of spacedsubstantially flat portions connected to each other by a curved portionso as to form on each of said fiat portions a free annular edge distantfrom said curved portion, said bending being performed by firstdeforming each of said substantially flat annular sheet metal membersinto a cup-shaped member having a bottom portion with a central openingand an annular rim projecting to one side of said bottom portion andjoined thereto along a curved portion, and by subsequently bending saidrim portion towards said bottom portion so as to form therefrom a secondcurved portion forming a continuation of said first-mentioned curvedportion and having the same radius of curvature as the latter and a flatportion substantially parallel to said bottom portion and overlappingthe latter; superimposing said thus bent members along a common axiswith said flat portions of adjacent members abutting against each other;and bonding said superimposed bent members along the free edges thereofto each other.

2. A method as defined in claim 1, wherein said U- shaped annularelements are formed from sheet metal and wherein said step of bondingsaid elements is performed by welding said elements along said freeedges thereof to each other.

3. A method as set forth in claim 2, and including the step of insertinginto said cup-shaped member a multipart form having an outer toricsurface, said bending of the rim portion being performed by bending saidrim portion onto said outer surface of said form, and subsequentlyremoving said multipart form from the formed sheet metal member.

References Cited UNITED STATES PATENTS 1,049,572 1/1913 Fulton 9234 X1,580,479 4/1926 Frankenfield 92--45 X 2,534,124 12/ 1950 Hasselhorn29-454 X 2,569,058 9/1951 Hobbs 29454 X 2,591,926 4/1952 Gibson et a1.29494 X 2,685,305 8/1954 Woods 29454 X 3,191,287 6/1965 Hall et al.29454 3,200,489 8/ 1965 Keeleric 29494 X CHARLIE T. MOON, PrimaryExaminer.

US Cl, X.R.

